The present invention relates to an exhaust gas purifying method and apparatus for an internal combustion engine, and more specifically to a method and apparatus for regenerating a particulate filter for trapping particulates present in exhaust gas.
An exhaust gas purifying apparatus having a diesel particulate filter (hereinafter referred to as DPF) is known. The DPF is adapted to trap particulates (hereinafter referred to as PM) present in exhaust gas emitted from an internal combustion engine, particularly, a diesel engine. When an amount of the PM trapped and accumulated in the DPF increases, the exhaust pressure upstream of the DPF increases to cause deterioration in the performance of the engine. Therefore, the DPF must be periodically regenerated by removing the PM accumulated therein.
Japanese Patent Application First Publication No. 2000-161044 discloses a method of regenerating a DPF. In this related art, the DPF is regenerated when an internal combustion engine is operated within a preset regeneration range. Even when the operation of the engine is out of the regeneration range, the DPF is continuously regenerated if the temperature of the DPF is a preset value or more. The related art aims for suppression of increase in fuel consumption required to raise the temperature of the DPF upon regeneration, by continuing the regeneration of the DPF even if the engine operating condition is out of the regeneration range.